A study on the relative distribution of mannoprotein and glucan in the cell wall of Saccharomyces cerevisiae has shown that the mannoprotein forms an external layer that determines cell wall porosity. The linkage between the different components of the cell wall will be the subject of future studies. The spatial controls that determine localization of the primary septum in yeast will be investigated with the help of a mutant that lays down septa at abnormal locations. Chitin synthetase from S. cervisiae has been highly purified by a novel procedure. Efforts are made to obtain antibodies against the enzyme to study its cellular localization and the relationship between chitin synthetase zymogen and active form. Experiments are also under way to clone the synthetase gene. Beta(1-3)Glucan synthetase, the enzyme that catalyzes the synthesis of the major structural polysaccharide in the Saccharomyces cell wall, has been studied in several fungi. The activation of the enzyme by nucleoside triphosphates was found to be conserved in species that are quite unrelated taxonomically. The kinetics of inhibition of the synthetase by the antibiotic, papulacandin, suggest that the enzyme exists in at least two different forms.